Copying method and apparatus with means to effect visible ray imaging and infrared ray transfixing or fusing

ABSTRACT

To improve the quality of the copies produced by a thermographic copier which relies on a tungsten lamp to thermally expose a heat sensitive member to an original which has some areas which absorb principally infra-red energy and others which absorb principally visible energy, a substantial portion of the infra-red energy emitted by the lamp is filtered out during the exposure process to thereby obtain a better balance between the infra-red energy and the visible energy. Toner particles containing materials which are absorbtive in the infra-red and visible spectrums are then applied to the sheet sensitive member to develop the image, and the developed image is thereafter fused on the heat sensitive member or transfixed onto a separate copy sheet under the influence of radiation from the same lamp but at a higher infrared energy level.

United States Patent [191 1111 3,909,613

Critchlow 1 Sept. 30, 1975 [54] COPYING METHOD AND APPARATUS 3.623.86911/1971 Allard 250/316 WITH MEANS TO EFFECT VISIBLE RAY IMAGING ANDINFRARED RAY TRANSFIXING OR FUSING [75] Inventor: James A. Critchlow,Macedon, N.Y.

[73] Assignee: Xerox Corporation, Stamford,

Conn.

[22] Filed: Jan. 2, 1974 [21] Appl, No.: 430,279

[52] US. Cl 250/319; 250/316; 355/3 DD [51] Int. Cl. G03C 5/16 [58]Field of Search 250/316, 317, 318, 319;

101/470, DIG. l3; 355/3 DD, 16, 110

[56] References Cited UNITED STATES PATENTS 2,916,622 12/1959 Nieset .1250/319 3,163,755 12/1964 Kotz 250/319 3,397,630 8/1968 Pratt 250/3193,447,872 6/1969 Pfaff 250/319 3,508,051 4/1970 Nichols 250/316 PrimaryE.\'aminerJames W. Lawrence Assistant E.\'aminerD. C. Nelms [57]ABSTRACT To improve the quality of the copies produced by athermographic copier which relies on a tungsten lamp to thermally exposea heat sensitive member to an original which has some areas which absorbprincipally infra-red energy and others which absorb principally visibleenergy, a substantial portion of the infrared energy emitted by the lampis filtered out during the exposure process to thereby obtain a betterbalance between the infra-red energy and the visible energy. Tonerparticles containing materials which are absorbtive in the infra-red andvisible spectrums are then applied to the sheet sensitive member todevelop the image, and the developed image is thereafter fused on theheat sensitive member or transfixed onto a separate copy sheet under theinfluence of radiation from the same lamp but at a higher infra-rcdenergy level.

10 Claims, 2 Drawing Figures US. Patent Sept. 30,1975 Sheet 1 of23,909,613

mumnn FIG. I

US. Patent Sept. 30,1975 Sheet 2 0f 2 3,909,613

FIG. 2

COPYING METHOD AND APPARATUS WITH MEANS TO EFFECT VISIBLE RAY IMAGINGAND INFRARED RAY TRANSFIXING OR FUSING DESCRIPTION OF THE INVENTION Inmost thermographic copying systems there is a tungsten lamp for heatingan original member which is held in contact with a heat sensitive memberthereby imparting a thermal image to the heat sensitive member. It hasbeen found that such systems encounter problems in making copies ofimages which absorb mostly (at least 90 percent) in the visible spectrumwhen they appear on an original either alone or along with infra-redabsorbing images. An example of such an image is a signed, typewrittenletter wherein (l) the type is of infra-red absorbing carbon black while(2) the signature is written in an ink which principally absorbsradiation in the visible spectrum such as a black or blue ball point orfelt pen. The root of the problem is that a tungsten lamp emits muchmore energy in the infra-red range than in the visible range. Forinstance, a tungsten lamp operating at 2,500 Kelvin has about 95 percentof its energy in the infra-red spectrum and about 5 percent of itsenergy in the visible spectrum, A tungsten lamp heated to 3300 Kelvinhas about 85 percent of its energy in the infra-red spectrum and aboutpercent of its energy in the visible spectrum. Thus the amount of heator energy absorbed by an infra-red absorbing image from the tungstenlamp will be much greater than that absorbed by a visible ray absorbingimage. If the visible spectrum absorbing image absorbs sufficient energyfor thermal imaging, then the infra-red absorbing image usually absorbstoo much energy with the result that it overheats, thereby preceding aballooning effect on the heat sensitive sheet. The term ballooningrefers to a thermal image increasing in size due to excessive heat beingtransferred to the heat sensitive member. In short, ballooning resultsin distorted characters and in many cases even overlap ping ofcharacters. Similarly, if the original image absorbs visible energy butlittle, if any, infra-red energy then the background areas of theoriginal may absorb sufficient infra-red energy to activate the heatsensitive member in the background areas, thereby causing a loss ofdefinition between the image and background areas. But if a sufficientamount of infra-red energy is filtered out so the ratio of infra-redenergy to visible energy emanating from the lamp is better balanced, theamount of heat absorbed by an infra-red absorbing image or background onan original as compared to an image absorbing mostly in the visiblespectrum is also better balanced. For instance, the ratio of energy(infra-red and visible) can be reduced to the extent which will allowsufficient heat to be absorbed by the inks on an original which absorbmostly in the visible spectrum for reproduction thereof while stillretaining sharp characters in the reproduction of the carbon blackimages on the same original and without the background absorbing anundue amount of infra-red energy. Thus, this will allow reproduction ofa broader range of colored images on an original.

It is therefore an object of this invention to produce a thermal imagesfrom original images, which contain images absorbing mostly in thevisible spectrum, by utilizing a tungsten lamp and filtering out asubstantial part of the infra-red energy emanating therefrom therebyachieving a more balanced ratio of infra-red energy to visible energy,whereby images absorbing mostly in the visible range will absorb enoughenergy to form a thermal image on the heat sensitive sheet, without anyinfra-red absorbing image becoming too hot to form a correspondingdistorted heat image on the thermal sensitive sheet or the backgroundareas of the original becoming too hot to melt the heat sensitive sheetin corresponding areas to affect the image definition.

Another object of the invention is to utilize a tungsten lamp in theaforementioned manner to reproduce thermal images from original imagesformed from noncarbon black or blue inks.

After a heat image is formed on the heat sensitive member, it isdeveloped with infra-red and visible absorbing developer materials whichwill utilize the total available energy emanated by the tungsten lamp toeither fuse the same to the heat sensitive material or to transfix(transfer and fuse) the same to a copy sheet.

It is a further object of this invention to utilize the same tungstenlamp for reproducing an original image by effecting a heat image thereofon a heat sensitive member utilizing a significantly reduced energyratio of infra-red to visible and for fusing a developed image onto theheat sensitive member or effecting transfixing of a developed image fromthe heat sensitive member to a copy sheet utilizing a substantiallyincreased amount of infra-red energy compared to the infra-red energyutilized during the imaging function.

Other objects of the invention will become apparent from the followingdescription with reference to the drawing wherein:

FIG. 1 is a schematic view of a copying machine showing an original anda heat sensitive member passing through an imaging and transfixing orfusing station; and

FIG. 2 is a schematic view similar to FIG. 1 only showing a developedheat sensitive member and a copy medium being passed through the machineto effect transfer of the developed image to the copy medium.

Referring to the drawings, the copying apparatus therein has four setsof guide moldings 4, 6, 7 and 8, the outer ends of each opening into theouter surface of the copying apparatus. The molding 4 serves as an inletguide for a sandwich of an original sheet 10 and a heat sensitive sheet12. The molding 6 serves as an outlet guide for the original sheet 10,and the molding 7 serves as an inlet guide for a copy sheet 14. The mold8 serves as an outlet guide for a sandwich of the heat sensitive sheet12 and the copy sheet 14.

The heat sensitive sheet 12, which may be considered for practicalpurposed to be transparent to infra-red energy comprises a support and aheat sensitive coating. For example, the support may be paper or anorganic film, such as a polyester film, cellulose acetate or triacetatefilm coated with a delayed tack adhesive which is normally hard andnon-tacky at room temperature, but which, upon being activated by heatto a tacky condition and subsequently cooled to room temperature,thereafter remains tacky for considerable periods of time varying fromat leat 30 seconds to several days or more depending upon the particularcomposition involved. Such delayed tack coatings are well known and canbe a mixture of discrete particles of resin, such as indene resin oresterfied resin and discrete particles of crystalline plasticizer suchas diphenyl or N-cyclohexyl paratoluene sulfonamide. The particles arebound together into the supporting film by a binder, such asstyrene-butadiene copolymer. Generally speaking, the crystallineplasticizer component of the mixture is in excess of the resincomponent.

An idler roll 16 and a conveyor mechanism comprising a drive roll 18, anidler roll 20 and a conveyor belt 22 are located at the inner end of theguide 10. A rotatably driven, radiation transparent, quartz cylinder 24is arranged on the frame of the copying apparatus to rotate in oppositedirections, and located within the cylinder 24 is a tungsten lamp 26.The idler roll 16 is arranged to contact the belt 22 to provide a nip 27therebetween for receiving and forwarding the sandwich of the originalsheet and the heat sensitive sheet 12. The cylinder 24 is arranged tocontact the belt 22 at the idler roll to form a nip 29 whereby a slightpressure between the cylinder 24 and the roll 20 is created to effect aslight pressure on a sandwich passing therebetween. Located downstreamof the idler roll 20 is a vacuum source 28 which serves to separate theoriginal from the heat sensitive member. A guide member 31 has a portion32 located and shaped to guide the original sheet 10 to a conveyormechanism 34, driven by a drive roll 35, which grabs the original sheetand conveys the original sheet through the guide 6 out of the machine.

A portion 37 of the member 31 directs the heat sensitive member to adeveloper station which comprises a housing containing ferromagnetictoner particles 36 and a magnetic brush 38.

The toner particles comprise thermoplastic particles pigmented withcarbon black or other infra-red absorbing dyes or pigments and mixedwith iron oxide particles. Preferably, the toner particles will absorbboth in the infra-red and visible spectrums. The magnetic developerbrush 38 is rotatably mounted on the housing and is so located to have aportion thereof rotatable through the toner particles 36 and anotherportion in engagement with the heat sensitive member 12 to develop thesame. A guide member 40 is located opposite the magnetic developer brush38 and has a portion 41 spaced from the outer surface of the developerbrush 38 approximately a distance corresponding to the thickness of theheat sensitive member 12 to ensure engagement of the toner particles 36with the heat sensitive member to develop the image thereon as the heatsensitive member passes the developer station.

Located within the copy guide 7 are a pair of nip rolls 42 which arelocated to grip the leading edge of the copy sheet 14 upon insertionthereof into the guide 7. Also, there is a guide 44 positioned to directthe developed heat sensitive sheet 12 and the copy sheet 14 into acommon passage 46 and to a conveyor mechanism comprising a belt 48 whichis trained around a drive roll 50 and an idler roll 52. The cylinder 24engages the belt 48 at the idler roll 52 to form a nip 54 therebetweeninto which the copy sheet 14 and the developed heat sensitive sheet arefed. At the proper time, the nip rolls 42 forward the copy sheet 14 intothe common passage 46 where the leading edges of the heat sensitivesheet 12 and the copy sheet 14 become aligned and form a sandwich whichis conveyed to the nip 54 between the cylinder 24 and'the belt 48 pastthe lamp 26. An idler roll 56 engages the belt 48 at idler roll 50 andcoacts with the belt 48 to move the copy sheet 14 and the heat sensitivemember 12 sandwich into the outlet guide molding 8 and out of themachine.

The lamp 26 is surrounded by a pair of filterreflectors 56 and 58. Thereflector 56 comprises a radiation transparent material such as quartzand is coated with an infra-red energy reflecting dichroic filter, andthe reflector 58 comprises a radiation transparent material such asquartz and is coated with a visible energy reflecting dichroic filter.Such dichroic filters are well known and can be designed to perform afunction depending upon the results desired as well as conditionsinvolved to carry out this invention, the filter 56 should be designedso that it reflects substantially all visible energy while passing orfiltering out sufficient infra-red energy to modify the ratio ofinfra-red energy to visible energy incident on the heat sensitive sheet12 such that images absorbing mostly (at least 90 percent) in thevisible range will absorb enough energy to form a corresponding heatimage on the heat sensitive sheet without any infra-red absorbing imagebecoming so hot that the thermal image thereof on the heat sensitive isdistorted and also without background areas of the original becoming sohot that background areas of the heat sensitive sheet are activated. Itshould be recognized that a given available ratio of infrared energy tovisible energy can result in an energy absorption ratio of carbon blackto non-carbon ink (black or blue) which is substantially lower than theenergy absorption ratio of carbon black to other non-carbon inks. Thismeans that a non-carbon black or blue ink can be copied much easier andproduce much better copies than other noncarbon inks. This, however,would cover most originals with signatures since either blue or blackink is utilized for signatures. Obviously, the lamp must be emanatingsufficient visible energy to effect a heat image by the mostly visibleabsorbing images. A tungsten lamp operating at 3,300 Kelvin is usuallysufficient for imaging. As will be seen, the filter coated reflector 56is shaped to focus the energy reflect thereby to the point of contactbetween the belt 22 and the cylinder 24.

The reflector 58, on the other hand, is shaped to focus the energyreflected therefrom toward the point of contact between the belt 48 andcylinder 2. The coating thereon preferably passes or filters out visibleenergy while reflecting substantially all of the infra-red energy.

A motor (not shown) is operably connected to drive the drive rolls 18,35 and 50, the cylinder 24 and the magnetic brush 38. This same motoralso is connected to a vacuum supply source providing vacuum toseparator 28. A separate motor (not shown) is operably con-' nected tothe nip rolls 42 for driving the same. The motors are operated by acontrol (not shown) which operates the machine as follows:

Referring to FIG. 1, the heat sensitive sheet 12 and an original sheet10, bearing an image absorbing mostly in the visible spectrum, togetherwith another image for absorbing infra-red energy absorbing imagethereon, are placed together and then inserted as a sandwich into theguide passage 4 and into the nip 27 between the rolls l6 and 18. A copysheet 14 is inserted into guide 7 and into the nip formed by rolls 42. Aswitch is actuated to start the control mechanism whereupon the conveyorbelt 22 and the idler roll 16 grab the leading edge of the sandwich andmove the same to the nip 27 between the cylinder 24 and the belt 22. Atthis time, the lamp 26 is energized and the sandwich is exposed theretoas it travels therepast to create a tacky image on the heat sensitivemember 12 corresponding to the image on the original sheet. The sandwichis moved downstream where the original and the heat sensitive sheet areseparated by the vacuum source 28. The original continues around theguide 32 to the conveyor mechanism 34 and out of the machine through theguide 6 while the heat sensitive member continues to the developerstation whereby the magnetic brush 38 dusts the tacky image with tonerparticles 36 to develop the same.

Referring to FIG. 2, the developed heat sensitive sheet 12 continuesbeyond the developer station and onto the guide 44 whereupon the controlsystem actuates the nip rolls 42 to bring the leading edges of the copysheet 14 and the heat sensitive sheet 12 into aligned engagement to forma sandwich which enters the nip 54 and is moved past the lamp 26 by thebelt 48 allowing the sandwich to be heated by infra-red radiation untila substantial portion of the toner particles become transfixed(transferred and fixed) to the copy sheet to provide a reproduction ofthe original image. This transfer occurs due to the pressure between thesheets effected by the pressure contact between the roll 52 and cylinder24 combined with a corresponding proper temperature. The sandwich isdriven out of the machine through the guide 8. The control system has acam system which is turned off the motors and the lamp 26 after thetrailing edge of the heat sensitive sheet, copy sheet sandwich is passedbetween the belt 48 and the idler roll 54. The operator of the machinethen removes the sandwich from the machine and separates the copy sheet14 from the heat sensitive sheet 12 to obtain his copy of the original.

Rather than transfer the developed image, the developed image may befused onto the intermediate. In this instance, the belt 48 may comprisea material to which melted toner particles will not stick.Alternatively, a release sheet could be substituted for the copy sheet14 with a heat sensitive sheet, release sheet sandwich being fed pastthe lamp 26. In this case, the release sheet will be of a material towhich the toner particles will not stick.

Rather than inserting a copy sheet into a slot in the machine, anautomatic paper feeder could be provided.

The control system and the components thereof for operating the machinein the manner described are all well known and well within the grasp ofone having ordinary skill in the art and therefore have not been shown.

What is claimed is:

l. A method for using a radiant source which emits substantially moreinfra-red radiation than visible radiation in thermographically copyingan original bearing an image which is principally absorbtive to visibleradiation; said method comprising the steps of bringing said originalinto engagement with a heat sensitive member to form a sandwich,

exposing said sandwich to radiation from said source to thermally impartsaid image to said heat sensitive member,

and filtering out a predetermined part of the infra-red radiationemitted from said source while exposing said sandwich, with saidfiltered out part being selected to prevent excessive heating ofinfra-red ab- 5 sorbtive areas of said original.

2. The method of claim 1 wherein at least 90 percent of the radiationabsorbed by said image is visible radiation.

3. The method of claim 2 further comprising the steps of developing theimage on the heat sensitive member with an infra-red absorbing material,and exposing the developed image to a substantially higher level ofinfra-red radiation from said source than was utilized while exposingsaid sandwich.

4. The method as recited in claim 3 wherein the developed image is fusedto the heat sensitive sheet when exposed to said radiation.

5. The method as recited in claim 3 wherein the de veloped image istransferred from the heat sensitive sheet and fixed to a copy memberwhen exposed to said radiation.

6. The method as recited in claim 3 wherein the exposure of a portion ofthe developed image to said radiation is simultaneous with the exposureof a trailing portion of said sandwich.

7. A thermographic copier comprising the combination of a radiant sourcewhich emits substantially more infrared radiation than visibleradiation,

30 an imaging station, and

means including dichroic filter for focusing radiation from said sourceonto said imaging station, said filter being selected to prevent apredetermined part of the infra-red radiation emitted by said sourcefrom reaching said imaging station without materially attenuating thevisible radiation.

8. The thermographic copier of claim 7 wherein said radiant source is atungsten lamp.

9. A thermographic copier comprising the combination of a radiant sourcewhich emits substantially more infrared radiation than visibleradiation,

an imaging station where images carried by an original are thermallyimparted to a heat sensitive member,

a fixing station where developed images on said heat sensitive memberare fused,

a first reflector having a dichroic filter-type surface coating forfocusing radiation from said source to said imaging station whilefiltering out at least a part of the infra-red radiation, and

a second reflector having a different dichroic filtertype surfacecoating for focusing radiation from said source to said imaging stationwhile filtering out at least a part of the visible radiation;

said first and second filters being positioned to surround said radiantsource.

10. The thermographic copier of claim 9 wherein said source is atungsten lamp.

1. A method for using a radiant source which emits substantially moreinfra-red radiation than visible radiation in thermographically copyingan original bearing an image which is principally absorbtive to visibleradiation; said method comprising the steps of bringing said originalinto engagement with a heat sensitive member to form a sandwich,exposing said sandwich to radiation from said source to thermally impartsaid image to said heat sensitive member, and filtering out apredetermined part of the infra-red radiation emitted from said sourcewhile exposing said sandwich, with said filtered out part being selectedto prevent excessive heating of infra-red absorbtive areas of saidoriginal.
 2. The method of claim 1 wherein at least 90 percent of theradiation absorbed by said image is visible radiation.
 3. The method ofclaim 2 further comprising the steps of developing the image on the heatsensitive member with an infra-red absorbing material, and exposing thedeveloped image to a substantially higher level of infra-red radiationfrom said source than was utilized while exposing said sandwich.
 4. Themethod as recited in claim 3 wherein the developed image is fused to theheat sensitive sheet when exposed to said radiation.
 5. The method asrecited in claim 3 wherein the developed image is transferred from theheat sensitive sheet and fixed to a copy member when exposed to saidradiation.
 6. The method as recited in claim 3 wherein the exposure of aportion of the developed image to said radiation is simultaneous withthe exposure of a trailing portion of said sandwich.
 7. A thermographiccopier comprising the combination of a radiant source which emitssubstantially more infra-red radiation than visible radiation, animaging station, and means including dichroic filter for focusingradiation from said source onto said imaging station, said filter beingselected to prevent a predetermined part of the infra-red radiationemitted by said source from reaching said imaging station withoutmaterially attenuating the visible radiation.
 8. The thermographiccopier of claim 7 wherein said radiant source is a tungsten lamp.
 9. Athermographic copier comprising the combination of a radiant sourcewhich emits substantially more infra-red radiation than visibleradiation, an imaging station where images carried by an original arethermally imparted to a heat sensitive member, a fixing station wheredeveloped images on said heat sensitive member are fused, a firstreflector having a dichroic filter-type surface coating for focusingradiation from said source to said imaging station while filtering outat least a part of the infra-red radiation, and a second reflectorhaving a different dichroic filtertype surface coating for focusingradiation from said source to said imaging station while filtering outat least a part of the visible radiation; said first and second filtersbeing positioned to surround said radiant source.
 10. The thermographiccopier of claim 9 wherein said source is a tungsten lamp.